The Accuracy and Efficiency of the Consensus Forecasts: a Further Application and Extension of the Pooled Approach
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Dis cus si on Paper No. 07-058 The Accuracy and Efficiency of the Consensus Forecasts: A Further Application and Extension of the Pooled Approach Philipp Ager, Marcus Kappler, and Steffen Osterloh Dis cus si on Paper No. 07-058 The Accuracy and Efficiency of the Consensus Forecasts: A Further Application and Extension of the Pooled Approach Philipp Ager, Marcus Kappler, and Steffen Osterloh Download this ZEW Discussion Paper from our ftp server: ftp://ftp.zew.de/pub/zew-docs/dp/dp07058.pdf Die Dis cus si on Pape rs die nen einer mög lichst schnel len Ver brei tung von neue ren For schungs arbei ten des ZEW. Die Bei trä ge lie gen in allei ni ger Ver ant wor tung der Auto ren und stel len nicht not wen di ger wei se die Mei nung des ZEW dar. Dis cus si on Papers are inten ded to make results of ZEW research prompt ly avai la ble to other eco no mists in order to encou ra ge dis cus si on and sug gesti ons for revi si ons. The aut hors are sole ly respon si ble for the con tents which do not neces sa ri ly repre sent the opi ni on of the ZEW. Non-technical summary The last decade has seen marked economic fluctuations in the major industrial countries, which regularly present business cycle forecasters with a challenge. In this paper we are interested in how professional forecasters managed to predict GDP and price developments during the last decade. To this end, we explore the accuracy and evolution of the Consensus Forecast for twelve industrial countries for the years 1996 to 2006. This pooled forecast has the main advantage that it offers monthly publications of revised forecasts for the current and the next year, so that an explicit revision process of 24 forecasts for every target year can be observed. The theoretical and econometric analysis is based on the framework of Davies and Lahiri (1995) and Clements et al. (2006). The latter employ a pooling procedure which permits the evaluation of all forecasts for each target variable over 24 horizons simultaneously. Adopting this methodology allows us to draw conclusions on evaluating systematic forecast bias and, by applying a test on the predictability of forecast revisions, on the efficient use of new information for all forecast horizons jointly. It is shown how the pooled approach needs to be adjusted in order to accommodate the forecasting scheme of the Consensus Forecasts. Furthermore, the pooled approach is extended by a sequential test with the purpose of detecting the critical horizon beyond which the forecast should be regarded as biased. Moreover, we show how the pooled tests for the predictability of forecast revisions can be improved by taking heteroscedasticity in the form of target year-specific variances of macroeconomic shocks into account. In the empirical part we first present results in the form of analytical confidence intervals surrounding the horizon-specific bias estimates which allow intuitive and meaningful interpretations. The test for common bias reveals that several countries show biased forecasts, especially with forecasts covering more than 12 months. These results partially confirm the presumption that the macroeconomic forecasts for the past 10 years were severely affected by the pronounced shocks in that period. The fact that for individual countries systematic biases can be observed by applying the Consensus Forecasts reveals that in these countries the forecasting industry on the whole was not able to cope with the shocks specific to the past ten years. Revisions of past months for GDP growth forecast have significant explanatory power for current revisions for almost all countries. For inflation revisions we find significant past revisions for some countries. Overall, our results imply that a lack of information efficiency is more severe for GDP forecasts than for inflation forecasts. The accuracy and efficiency of the Consensus Forecasts: A further application and extension of the pooled approach October 2007 Philipp Ager GSE, Universitat Pompeu Fabra, Barcelona Marcus Kappler1 Centre for European Economic Research (ZEW), Mannheim Steffen Osterloh Centre for European Economic Research (ZEW), Mannheim Abstract: In this paper we analyze the macroeconomic forecasts of the Consensus Forecasts for 12 countries over the period from 1996 to 2006 regarding bias and information efficiency. A pooled approach is employed which permits the evaluation of all forecasts for each target variable over 24 horizons simultaneously. It is shown how the pooled approach needs to be adjusted in order to accommodate the forecasting scheme of the Consensus Forecasts. Furthermore, the pooled approach is extended by a sequential test with the purpose of detecting the critical horizon after which the forecast should be regarded as biased. Moreover, heteroscedasticity in the form of year-specific variances of macroeconomic shocks is taken into account. The results show that in the analyzed period which was characterized by pronounced macroeconomic shocks, several countries show biased forecasts, especially with forecasts covering more than 12 months. In addition, information efficiency has to be rejected in almost all cases. Keywords: business cycle forecasting, forecast evaluation, Consensus Forecasts JEL-Classification: C 52, E 32, E 37 1 Corresponding author. P.O. Box 103443, D-68034, Mannheim, Germany, E-Mail: [email protected]. For helpful feedback, we thank François Laisney and the audience at the International Workshop in Economics and Finance (IWEF 2007) at Tripolis, Greece, 16 June 2007. All remaining errors are the responsibility of the authors. 1 Introduction The last decade has seen marked economic fluctuations in the major industrial countries, starting from the new economy boom beginning in the mid-nineties, followed by a lengthy downturn due to the burst of the dot-com bubble and accelerated by a number of events like 9/11 and concluding with the recent economic recovery. Such economic fluctuations regularly present business cycle forecasters with a challenge. In this paper we are interested in how professional forecasters managed to predict GDP and price developments during the last decade. To this end, we explore the biasedness and efficiency of the Consensus Forecast for twelve industrial countries for the years 1996 to 2006. The Consensus Forecast is a pooled forecast based on a monthly survey among professional forecasters from the respective country. Due to its aggregation it is often regarded as the market’s opinion on the future development of the economy. One main advantage the Consensus Forecasts offer to our analysis is that, because of the monthly publication of revised forecasts for the current and the next year, an explicit revision process of 24 forecasts for every target year can be observed. Moreover, due to international standardization regarding methodology and date of publication, these forecasts are highly relevant for international comparisons. This kind of forecasts has received increasing attention in the forecast evaluation literature in the past years, starting with Loungani (2001) who compares the Consensus Forecasts for industrialized and developing countries in the years 1989-1998 regarding accuracy, biasedness and efficiency. In a recent work, Batchelor (2007) addresses similar questions by analyzing the bias of the Consensus Forecasts in the years 1990-2005. He finds evidence for overoptimistic GDP forecasts in Japan, Germany, France and Italy, and no evidence for a bias of the inflation forecasts. The biasedness of individual forecasters is a very popular object of investigation (see, for instance, Batchelor, 2001, for OECD and IMF forecasts; a survey on national studies can be found in Fildes & Stekler, 2002). The frequently found characteristic of systematically biased forecasts is usually attributed to error sources on the individual level such as model misspecifications, herding or political biases (see Stekler, 2007, for an overview). However, the studies applying the Consensus Forecasts use a pooled forecast, where these individual biases are typically expected to cancel out. Therefore, the biases found by Batchelor (2007), which are unequal in size between the countries, do not hint to irrationality on the individual level, but can be attributed to a common wrong dealing with 1 country-specific external influences such as declining growth trends, which were shared by all forecasters in a country. As the Consensus Forecasts constitute a fixed-event forecast, with every target year forecasted separately from 24 horizons before, it complicates the empirical analysis. Batchelor (2007) applies a conventional approach, by testing single forecast horizons individually for biasedness. This may be accomplished by the Mincer-Zarnowitz test (Mincer & Zarnowitz, 1969), or by a more general t-test as introduced by Clements (2005, p.6). However, this kind of test has one decisive weak point for the high-frequency fixed-event forecasts of the Consensus Forecasts: Either all 24 horizons are tested individually, and the comparative results lose in explanatory power due to the complexity of 24 tests with potentially different results. Or, as done in Batchelor (2007), only selected horizons out of the 24 available are tested and compared, but then a loss of information occurs. To cope with this problem, in this paper a cutting edge pooling method proposed by Clements et al. (2007) and Davis & Lahiri (1995) is applied. The second question of this paper, the efficiency of the forecasts, has received more attention in the literature regarding the application to fixed-event forecasts in the form of the Nordhaus test (Nordhaus, 1987) on the unpredictability of forecast revisions. Further applications of this methodology on the pooling of fixed-event forecasts over different target years can be found in Clements (1997) and Harvey et al. (2001). Isiklar et al. (2006) are the first who analyze Consensus Forecasts for 18 industrialized countries from 1989 to 2004 and who consider a pooling over several countries. Again, a pooled approach based on the works of Clements et al.